Energy crisis and environmental pollution have become great bottlenecks to global economy development. Energy-saving and environment friendly vehicles provide a good way to release energy pressure and reduce environmental pollution. Hybrid vehicles have the advantages of both internal-combustion engine vehicles and pure electric vehicles, such as low gasoline consumption, less emissions and long mileage, and therefore would be a feasible solution to energy crisis and environmental pollution.
Parallel hybrid vehicles have two power sources, an engine and a motor. A Hybrid Control Unit (HCU) determines a working mode based on a current operation state of the vehicle, and sends a power request and a mode request to the engine and the motor, respectively. Control units of the engine and the motor control respective power sources according to an instruction of the HCU, to meet requirements of the whole vehicle.
When the hybrid vehicle sends a torque request for auxiliary driving, electricity generating or regenerative braking, the HCU limits the torque request according to the status of the motor, battery and engine. If more than two of the torque requests above are present, the HCU is to arbitrate the torque requests, then send a torque request to the motor. Therefore, how to limit the torque requests and whether torque arbitration mechanism is suitable will affect performance of the hybrid vehicle.